Screw driver



May 1',1927 w. HERRMANN 8' v scREw DRIVER Filed nay 1e. 1924 William r sr'ryv'uznn afg www. AW.,-

, 55 mw -M,

Patented May 10, 1927.

j. UNITED*STATES` PATENT OFFICE. j

WILLIAM HERRMANN,

oF CHICAGO, ILLINOIS.

SCREW DRIVER.

Application filed May 1e, 1924. `serial No. 713,696.

My invention relates to screw drivers.

rllhe fundamental object ofthe invention is to provide a screw driver embodying an improved and simplified construction of holding means for holding the screw to be driven. A screw driver ofthis ty e is advantageous and often a necessity for driving screws in overhead surfaces, in cramped corners and in other places difiicult of access.

`@ne of the particular objects of my invention is to provide improved means for giving a lateral movement to the screw holdj ing jaws for openingandzclosing the same.

Another object is to provide `improved nrountingl means for these screw holding jaws which will permit of a limited longitudinal movement thereof relative to the screw driver bitI for enablingthese jaws to retract from the end `of the bit and clear the head of the screw when the screw is to be driven home. j l

Other objects will be apparentfrom the following description taken in connection with the accompanying drawings in which:

Figure 1 is a longitudinal sectional view through the operating parts of a preferred form of my invention, showing` the jaws in the position of holding a screw. Y.

Figure 2 is a similar view showing the jaws moved upwardly along the bit shank.

Figure 8 is a fragmentary sectional view showing the operating parts as viewed at right angles to Figure 2.

Figures` is a transverse sectional view taken approximately on the plane of the .line fle-lf of Figure2, and i j Figures 5. and G are views of the` sheetmetal stamping from vwhich each screw holding jaw is formed. j

The deviceis assembled about a central shank G which is preferably of cylindrical form. j At one end the shank is flattened out on lopposite sides to form the tapered bit 7 adapted to engage in the kerf or slot 8 of the screw or bolt 9. At its opposite end the shank extends into a suitable handle l1 rigidly secured thereto. n

The screw holding means comprises two fingers 12-12 supported on opposite sides of the shank 6. The outerends of these fingers arefcurved` inwardly to form gripping jaws 1l` for engaging under vthe head 10 of the screw or bolt, 9. These jaws 14 preferably have inclined jaw surfaces substantially as shown to grip the tapered un- 12 at points intermediate their' ends.

`gripping fingers are positively confined in der side of the head of a wood screw 0r the straight under side of thev head of a machlne` screw. Directlyabove these jaws small abutment shoulders 15 project inwardly from each finger for engaging the top of the screw head. 1

These gripping fingers are adapted to be rocked into and out of gripping engagement 4 with the screw head by pivoting the lingers at points intermediate their ends and having cam surfaces engage either the upper' or lower ends thereof to rock the Ajaws 14 towards or away fromthe bit 7. This pivotal or rocking support occurs about a collar 16 loosely mountedon the shank 6. On diametrically opposite sides this collar is formed with two longitudinally extending slots 17 which laterally confine and guide the rocking lmotion of the gripping fingers 12. Intermediate their ends, these slots 17 are formed with inwardly extending recesses or holes 18 for receiving pivot lugs 19 which project inwardly from the gripping 'fingers The seating of these lugs 19 inthe bottoms of these depressions 18 affords a sim- `ple and inexpensive rocking support for each gripping finger'. `Then once assembled, the

S5 the slgts 17 and in the pivotal depressions 18 by -the outer sleeve 21 which embraces and houses the greater'part of both fingers. The fingers are thus compelled to move with the linear movement of the collar 16.

The collar 1G is balanced on the shank 6 between two springs 22 111111,23. The lower end of the lower spring 22 abuts a collar 2frigidly secured to the shank, and the upper end ofthe other spring extends into the counterbore 25 in the sleeve closure cap 33, which I shall presently describe. T ie upper spring 23 is preferably of greater compression strength than the lower spring.

The enclosing `sleeve 21 is preferably of brass tubing or other light stbck and has its lower end swaged or reduced down to form the long tapered neck 27 forming an internal4 annular cam surface 28. This cam surface is adapted to co-operate with the long sloped cam surfaces 29 formed on the outer sides of the gripping fingers 12 directly above the jaws 14. then relative movement between the gripping fingers 12 and the sleeve21 brings the finger cam surfaces 29 down into the constricted end of the` tapered neck 27 the gripping jaws ,are

forced inwardly into firm `gripping engagement with the screw head.

The other ends of said gripping fingers are formed with curved or tapered cam surfaces 31 which are adapted to cri-operate with an internal annular cam surface 32 formed in the closurecap 33. This closure cap is threaded for screwing intotlie threaded upper end of the sleeve 21, this open end of the sleeve being slipped ovei the parts 12 and 16 in the assembly of the device. The Y:ap may be providedwith a knurled flange 34 for ease of gripping the cap and the sleeve. lt will be apparent'that when the sleeve'21 is thrust forwardly the movement of the interna-l cam surface 32 over the cani tails 31 on the fingers will rock these ends of the fingers together and separate the gripping jaws 14.

Normally, the pressures ofthe two springs 22 and '23, which are both reactive against the stop collar 24, hold the slidable vpivot collar 1G with its giipping :fingers raised and also hold the operating sleeve 21 in a raised position. In this position the jaws 'la are retracted back from the end ofthe bit 7 so that they will clear the head of any screw and `not interfere with the ordinary operation of the screw driver where no screw gripping function is desired.

Then it is desired to grip the screw to be driven, the sleeve 21 is thrust forwardly along the shank 6. This, acting through the spring 23 of greater compression, shifts the collar 1G outwardly along the shank 6 and brings the gripping jaws 14: out approximately as far as shown in Figure 1. The forwaid thrusting motion of the sleeve 21 exceeds that ofthe gripping fingei'rs 12 so that the cam surface 32 overruns the ends 31 of thegripping fingers and separates the jaw ends. The` screw is now placedbetween the jaws with the bit 7 engaging in the. kerf 8. The operating sleeve is now permitted to come back under its own spring pressure, and during'this return movement of the sleeve the gripping jaws 111 may be pinched inwardly by the fingers'of the oper ator against the sides of the screw head to prevent return vmovement of the jaws with the sleeve; or the sleeve may be moved sharply backwardsfor automatically closing the jaws on the screw head. This brings the lower tapered cam surface 28 upwardly along the sloped surfaces 29'of the fingers 12 and cams thesefingers 'inwardly `against the screw head. AAn additional upward pull may be given the sleeve' 21 relative `to the handle 11 to wedge the cam surface 28 against-'the gripping fingers andfirinly hold these fingers against the screw head. The screw is now held ready 'for Y 'driving Then the screw head approachesthe surface into which the screw is'being driven 'and it is desired'to retract thegripping fingers to permit the head to be driven down flush with or into the surface, the operating sleeve 21 is thrust forwardly along the shank 6. This first vreleases the wedge grip between the cani surface 28 and the gripping fingers 12 and continued motion thereafter brings the upper cani surface 32 down over the tail ends Blof-the fingers, forcibly separating the jaws from the screw head if they havenot already released the screw head. Releasing of the sleeve 21`tlienpermits the springs to thrust the sleeve backwardly along'the shank and to raise the gripping jaws to a. position where they entirely clear the screw head. The screw can now be driven vhome without any interference from thegripping fingers. t

The sleeve 2l and fingers 12 are now in their normal positions first mentioned and the gripping of another screw is a repetition ofthe foregoing operation. Y

The gripping fingers 12 may be punched and shaped outof solidi-od stock, or may be inade up as sheet vmetal stampings. The latter `process is shown in AFigures 5 and (3. The finger is first blanked out of sheet metal stock as shown in Figure The pivot lug or lugs 19 are formed as laterally projecting ears on the edges of the fiat blank,

and the gripping jaw 1d is blanked out as the flaring slotted end shown. The lugs 19 are then folded along the lateral 'edges of the blank to bring the two lugs 19 into parallelism, and the lower end is slightly curved 'to give a curved inner face to the gripping jaw 14. Tf desired the lugs 19 maybe vleft projecting outwardly from the sides of the blank, and the shiftable block 16 be slottedtransversely of the slots 17 for providing kerfs for receiving these lugs.

vI claim:

1. Tn a screw driver ofthe class described, the combination of va shank, a pair of springs, one of which abuts againslja fiange on said shahlqa collar slidable on said shank between said springs,^gripping fingers con- 'nected to said collar, and an operating vsleeve engaging the other spring slidable over said collar and said gripping fingers for rocking Asaid fingers relative to said collar.

2. In a screw drivei'of the class described, the combination of a shank, acollar slidable on said shank, gripping fingers connected to said'collar, a shoulder on said shank, a spring between said shoulder and said collar, a sleeve engaging over said collar and said fingers, a spring between said collar and one end of said sleeve, and cani surfaces on the upper and lower ends of said sleeve adapted to engage the ends of 'said ngers for camming said fingers vinto and out of engagement with the screw head.

3. In ascrew driver of the class described, the combination of a shank having a bit at llO one end and a handle at the other, a collar slidable on said shank, gripping fingers sliding with said collar, a shoulder 0n Said shank, a spring between said shoulder and said collar, a reciprocable sleeve engaging over said collar andsaid fingers, a spring between said collar and one end of said sleeve, said sleeve having a surface adjacent one end adapted to engage the ends ofsaid fingers for oamming said in ers into and` a surface adjacent its other en for camming said fingers out of engagement with the screw head.

In witness whereof, I hereunto subscribe my name this 6th day of May, 1924.

WILLIAM HERRMA'N N 

